Some Graphite queries are very ineffective. Tools like Seyren multiply this effect every minute making
lots of ineffective queries and overloading your cluster. Moira relies on the incoming
metric stream, and has its own fast cache for recent data.

Support for (almost) all Graphite functions

Graphite function library (carbonapi) is embedded directly into Moira source code. You can use any
function and get predictable results, like in your Graphite or Grafana dashboards.

Support for custom expressions

If simple warning/error threshold is not enough, you can write flexible govaluate expressions to
calculate trigger state based on metric data.

Tags for triggers and subscriptions

When several teams/services share one monitoring tool, it is essential to provide some way of
filtering triggers and subscriptions in the UI. Moira has a flexible tag system.

Extendable notification channels

Moira supports email, Slack, Pushover and many other channels of notification out-of-the-box. But you can always
write your own plugin in Go and rebuild Moira Notifier microservice.

Sometimes one of your triggers goes mad and switches back and forth between states, sending you
hundreds of notifications. Sometimes you just ignore and delete all messages, accidentally also
deleting one that is actually important. Moira tries to protect you with a feature called
throttling. It’s simple: if one of your triggers starts to send over 10 messages per an
hour, Moira limits this trigger to one message per 30 minutes. Alerts from this trigger are
combined, and not lost - just packaged into a single message.

By default, Moira stores metric history for one hour. This ensures performance under heavy load.
You can tweak this in config file, but note that performance will degrade.

In order to reduce database load, Moira checks every single trigger at most once every 5 seconds.
Probably, your metrics arrive once every minute, so you really won’t notice this limitation.
You can also tweak this in config file.

Filter is a lightweight service responsible for receiving lots of metric data in Graphite
format. It filters received data and saves only metrics that match any of user triggers. This
reduces load on all other parts of Moira.

Checker is an application with embedded Graphite functions. Checker watches for incoming
metric values and performs checks according to saved trigger settings. When state of any trigger
changes, Checker generates an event.